Field of Invention
The present invention relates to devices and methods for determining knock in internal combustion engines.
Description of Related Art
In general, a knock determining device for an internal combustion engine determines the occurrence of knock on the basis of peak positions or peak intensities of vibration waveforms detected by a knock sensor for detecting vibration of a cylinder block.
However, it is difficult to discriminate between knock and noise and to accurately detect knock since various types of background engine noise, for example, noise generated when fuel injection valves are seated or the driving noise of an adjustable valve device, are generated in an internal combustion engine.
To solve this problem, an existing device determines the occurrence of knock based on peak intensities in specific frequency bands by excluding those frequency bands in which the background engine noise occurs, including the noise of fuel injection valves, to obtain a subset of the specific frequency bands in which peaks exist when knock occurs but not when other driving noise occurs. As a result, noise generated when the fuel injection valves are seated, for example, is prevented from being falsely detected as knock. However, when knock occurs having peaks in frequency bands other than the specific frequency bands, and particularly in frequency bands that were excluded due to the presence of engine noise, the occurrence of knock cannot be detected by such a device. That is, the knock detection performance is disadvantageously reduced compared with the case where the specific frequency bands are not limited by the exclusion of those frequency bands in which background engine noise occurs.